Automatic bottle openers are know that are applied to a wall or to a table or are also directly placed on the neck of the bottle and are held there tight during the opening operation. Allen. U.S. Pat. No. 4,253,351.
In this type of bottle opener, the worm-screw does not penetrate the closure due to the pushing effect and the rotary movement produced by the operator's hand but rather because it is pushed to penetrate with only a downward axial movement and the rotation is imposed as it is constrained, during this movement, to cross a nut or nut screw, that forces it to rotate.
With this type of bottle opener, it is possible to distinguish two families; in the first, as that described by Allen U.S. Pat. No. 4,253,351, it is the worm-screw itself that crosses the nut to assume the rotary movement; in the second family, the one that we shall be considering, the worm-screw has the sole function of penetrating the closure in order to extract it and the rotary movement is assumed by means of a complementary helicoidal screw integral with the worm, positioned on the same axis.
In the bottle openers where the worm crosses the nut (Allen), to complete the opening operation and release the worm from the closure, two complete movements are necessary from the top downwards and vice-versa.
Instead, in the type of bottle openers that are to be considered and described and where the invention will find an application, the worm makes a single movement, first downwards to penetrate the closure, then upwards, with a single operation to extract said closure and proceeding in the same movement to release it after from the closure.
This second method allows a faster operation that is safer, less complex, with less breakages and improved simplicity of construction, however it presents the disadvantage, as already mentioned and until now unresolved, that if in the extraction stage the closure does not offer sufficient friction on the worm, the worm is unthreaded from the closure that remains perforated in the bottle.
Said friction is necessary with respect to the worm, in the prolongation of its upward axis, it is fixed to a movable support by means of an idle system, a bearing, two flanges etc. that do not offer any type of stop to the rotation of the worm.
The need for the worm-screw to be free to rotate in both directions derives from the fact that first, when it is pushed into the closure it must rotate clockwise to penetrate it and then once the closure has been extracted from the neck of the bottle it must still be free to rotate in the opposite direction, namely anti-clockwise, to be able to release itself from the closure itself.
As long as it concerns cork closures, the extraction operation is generally successful. However, in the last few years, new types of closures have appeared on the market, namely synthetic closures: (Silicone plastic material etc.). These closures offer the advantage of being odourless and not having unpleasant flavours, they generally cost less and their use is increasingly widespread.
In general, these closures are viscid, slippery and impose less friction on the worm-screw than that normally imposed by cork, therefore during the opening operations, the worm penetrates the closure but when the movement is inversed and pushed upwards in order to achieve extraction, the worm, not disposing of any other way of stopping in rotation can be unthreaded with the anti-clockwise rotary movement and the closure remains perforated but in the neck of the bottle and therefore opening does not take place.